When a mobile station (MS) operating in a cdma2000 communication system attempts to originate a call with a wireless infrastructure, and in particular a base station (BS) included in the wireless infrastructure, via a first radio frequency (RF) band, such as an 800 megahertz (MHz) band, for the purpose of setting up a call, the BS is not aware of the RF capabilities of the MS. The capabilities of the MS, such as the RF bands supported by the MS, as well as an MS identifier (mobile ID), such as an International Mobile Subscriber Identity (IMSI), associated with the MS and a listing of services subscribed to by the MS, are typically stored in a profile of the MS in a Home Location Register (HLR) located elsewhere in the wireless infrastructure.
In response to receiving a request to originate a call from the MS, the BS determines whether the first RF band is congested, for example, whether any traffic channels are available in the first RF band, whether the RF band is operating at or near a maximum power load, or whether the Walsh Codes are exhausted. When the first RF band is not congested, the BS assigns an available traffic channel to the MS. In parallel with the traffic channel assignment, the BS conveys an A1 message, typically an A1 CM Service Request message, to a mobile switching center (MSC) servicing the BS requesting authentication and verification of the MS. In response to receiving the Origination Request, and if the profile is not already stored in a Visitor Location Register (VLR) associated with the MSC, the MSC downloads the entire profile of the MS from the HLR and stores the downloaded profile in the associated VLR. The MSC then verifies and authenticates the MS based on the downloaded profile and informs the BS whether to proceed with, or tear down, the call.
When the first RF band is congested, the BS terminates the access attempt of the MS and releases the call. In such an instance, the BS never communicates with the MSC. Furthermore, the process whereby the BS contacts the MSC and waits for the MSC to download the profile of the MS and to inform the BS whether to proceed with the call consumes an inordinate amount of time and would introduce a call setup delay that is unacceptable to system operators. If the MS is a single-band MS, the user of the MS will have to retry accessing the communication system at a later time. If the MS is a multi-band MS that is capable of operating in multiple RF bands, the MS may then initiate an access attempt of the communication system via a second RF band, such as a 2.1 gigahertz (GHz) band or a 1.9 GHz band. However, requiring a multi-band MS to re-initiate an access attempt in a second RF band is time consuming and is frustrating to users of such MSs.
Therefore a need exists for a method and an apparatus that determines an MS's RF band capabilities with minimum delay upon an initial call origination attempt and that re-directs a multi-band MS to a different RF band when an accessed RF band is congested.